Journey North's Elizabeth Howard made some observations at a House Wren nestbox on June 19, 2002. She peeked into the box and saw that there were 5 young wrens at the time. Two days after she made these observations, the babies flew from the nest for the first time.
- How many days old were the babies on June 19th? Hint: find out how it takes for nestling House Wrens to fledge at:
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Elizabeth wrote the exact time whenever one of the adults came and fed the babies. First look at the data she collected during a half hour period, and then answer the following questions.
-
In 30 minutes, how many times did the wrens feed
their young?
-
On average, how many minutes did the nestlings have
to wait between feedings?
-
Assuming both mother and father did the feeding
equally, how many minutes did each bird take to find food and
deliver it back to the nest?
- How many times did the adults feed their young that day, if we assume they fed them at the same rate from sunrise to sundown? (Hint: Elizabeth made her observations near Lake Minnetonka in Minnesota.)
Discussion Questions
-
How do wrens find food so fast!? Elizabeth searched
throughout the woods and in the grass and couldn't find a single
spider, caterpillar, beetle, etc. How many insects can you find
in five minutes?
- The white margins on edges of babies beaks are very noticeable. These gape
marks are conspicuous in many baby birds. What are some
reasons why they might have them? Why are the markings paler--often
white--in cavity nesting birds than in species that nest in other
places?
- Elizabeth noticed that the male seemed to be gone
much longer than the female, and he brought back more "impressive" food
items, ie larger ones. In contrast, the female was more protective
and tended
to scold Elizabeth at the nest much more vigorously. Why do you
think the birds might have broken down their chores like this?
- Ornithologists, averaging data from many House Wrens over many years, say that a pair of House Wrens feeds older nestlings about 25-30 times per hour. These wrens fed their babies at twice that rate during the half hour Elizabeth was keeping records. Think of as many reasons as you can that Elizabeth's data is different from the average.
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